Parallelism is Relative
by NymboDerp
Summary: Sena and Tsuna are too alike, though really, that could've been attributed to how closely related they were to each other. But have you ever considered a scenario in which Tsuna introduces his cousin to his Guardians? Or one in which Sena introduces his cousin to his strange Amefuto-obsessed friends? Well, you'll find out here! AU, TsuSe are cousins, no specific pairings. Two-shot.


**A/N:** You can't make me believe that Sena and Tsuna aren't related.

Also, Sena's got straying eyes for shy and cute girls. Even if he's more than attached to his Amefuto-men.

Published: 15 Aug 14

Edited: 16 Aug 14

* * *

It was time for their annual family get-together, and Sena honestly wasn't looking forward to it.

He hated having to meet and greet all of his extended family, especially the ones from his father's side. His dad was the second youngest of five children, and he had more than enough cousins (and _their children_, considering how his eldest uncle had three thirty-plus year old children) than he'd ever wanted to deal with. They were all snobby and rude, and they'd only ever stopped putting Sena down after it had been revealed that yes, Sena was _that_ Eyeshield 21, and yes, it wasn't a hoax, here are the videos to prove it!

His mother's side, thankfully, wasn't all that bad. His mother had only had one sister, who had only one child, who was _thankfully_ the same age as him. Nana-oba-san was extremely sweet, and she was the one aunt that Sena loved to meet time and over again—and not to mention, Tsuna, his cousin, was the one person who could empathise with him over how useless they both were.

So when they'd arrived at the restaurant that they were to gather in, Sena had immediately ditched his parents (I want to look for Tsuna-kun, mum!) and searched for his cousin.

"Tsuna-kun! There you are!" He called out in relief when he saw his cousin's familiar, spiky hair. Tsuna's face split into a happy grin, and Sena quickly walked to his side. Greeting him with a tight hug, he finally let go to look his cousin over form head to toe.

He looked… strangely good now. Healthier, and happier. Had something happened to him in the 12 months they'd been apart?

"Ne, Tsuna-kun, you look a lot different… has something good happened to you?" Sena asked with a grin. "Maybe a new girlfriend? Finally got above 80% on your maths test?"

Tsuna laughed, before nudging him lightly. "I was going to ask the same thing to you, Sena!" Giving him a teasing poke in the side, he then said, "But really, I forgot to congratulate you on winning the Christmas Bowl! I was watching the match while it played live…"

Sena let out a contented smile at the thought of the game. The Teikoku Alexanders, while it had been the most physically exhausting game he'd ever played, he'd never felt so good about himself when they'd realised that they had won against the champions of Japan—and Sena had defeated _the original Eyeshield 21_.

"Thank you, Tsuna-kun… I still can't believe that we – the Deimon Devil Bats – managed to do that!" He exclaimed, scratching the back of his head awkwardly. "Well, you know what's been happening in _my_ life… so what's up with you?"

He looked up at Tsuna—realising only then that Tsuna wasn't alone. Blushing in embarrassment, he couldn't help but glance curiously at the people who were surrounding him.

He had quite the collection of boys around him – all of them much taller and strong looking compared to both Tsuna and himself, save for two, who were really just children. Not to mention he had a really cute girl next to him, who was carrying the aforementioned children.

"Well, I've got a whole bunch of friends now!" Tsuna said with a nervous laugh, gesturing at the people behind him. One of them had a scary glower on his face, and the one next to him laughed in a sinister manner—only for the girl to send him a slight frown, making him stop. "I'll introduce you, Sena!"

Sena gave the girl a nervous look – she was _really, really pretty_ – before he nodded. "Alright then…"

Tsuna beamed at him, and slung an arm around Sena's shoulders, pulling him closer to the group. "This is my favourite cousin, Kobayakawa Sena-kun. He's the American footballer I've been showing you guys every so often – the Eyeshield 21 guy?"

"I-it's nice to meet you!" Sena quickly blurted out, managing an awkward bow towards them.

Tsuna grinned, before gesturing with his hand towards a silver-haired man with handsome Eurasian features. Sena couldn't help but wonder if his silver hair was the result of dye, or of premature aging.

"This one's Gokudera Hayato-kun. He's the first of my best friends, and he's sort of like my right hand man," he added with an ironic chuckle. "Forgive him if he's a little loud – he really can be quite a firecracker at times!"

Gokudera didn't seem to mind the teasing, merely greeting Sena with an enthusiastic, "It's great to finally meet the Juudaime's family! I can definitely see the family resemblance between you two!"

"Now this big guy's Yamamoto Takeshi-kun. He's a baseball player, but he's also the best kendo-master I've met so far," Tsuna continued, patting Yamamoto on the bicep—probably because that was the easiest part of him that Tsuna could reach. He really was tall, but not as tall as Kakei—thank God. "He's really nice, and I'm sure you two will get along!"

Sena gave Yamamoto another bow, giving him a nervous smile.

Yamamoto laughed boisterously. "You don't need to be so polite, Sena-kun! You don't mind me calling you that, right?" He asked, even as Sena nodded quickly. "My dad runs an amazing sushi bar in Tokyo, so come over whenever you want. I'll be sure to ask him to give you some free service!" He added, his grin putting Sena at ease.

Wide-eyed, Sena couldn't help but wonder if Yamamoto was the big brother-figure that Sena and Tsuna never had.

Tsuna smiled in relief when it seemed that Sena was taking to his friends, quickly introducing him to Hibari-kun and Mukuro-kun in turn, making their introductions brief in case they ended up chasing his cousin away. He knew that Hibari and Mukuro could be scary even on the best of days.

Hibari sniffed contemptuously at Sena, obviously dismissing him as a threat, while Mukuro kept his heterochromatic eyes fixed on his cousin, almost as if he were prey.

Tsuna narrowed his eyes slightly, shaking his head decisively. Mukuro was not to touch his cousin at all!

There was a moment where the boy and his friend stared at each other with such intensity that it caused everyone to take a step back, unwilling to get involved in the silent war between them.

Finally, Mukuro looked away with a soft "fuu…"

Tsuna smiled triumphantly at his victory, before turning to the next of his Guardians. However, he wasn't fast enough to stop the white-haired boy from talking first.

"I am EXTREMELY happy to meet you, Tsuna's cousin!" Ryohei yelled boisterously, stepping forward with a wide grin on his face. "I'm Sasagawa Ryohei - but you can EXTREMELY call me nii-san!"

Sena's eyes widened a second time, and he couldn't help but wonder if Ryohei was the big brother-figure that Sena and Tsuna never wished they had.

"S-sure...?" Sena responded after a moment's respite, though he still looked rather shell-shocked by Ryohei's rather _explosive_ introduction.

Tsuna laughed nervously, taking hold of Sena's arm to capture his attention again. "Now, Sena, this is Dokuro Chrome-san. She's holding onto Reborn and Bovino Lambo-kun," he introduced, gesturing at each of them in turn.

Though Sena's eyes were fixed upon Chrome and her pretty face, he could see that Reborn looked around 8 years of age and was by Chrome's side, holding her hand rather sedately. Lambo, however, was squirming in Chrome's other arm, trying to break free to wreak havoc.

"N-nice to meet you, Sena-kun… Tsuna-kun has told us a lot about you," Chrome greeted in a voice that was just as pretty as her face, and that made Sena blush furiously. He'd never been so _captivated_ by such a pretty girl, and the fact that she was _talking to him_, willingly too…!

"I- I hope it wasn't anything too bad," Sena stammered out after a moment's silence, all too aware of Tsuna's amusement.

"Let Lambo-san go! Lambo-san wants to eat _now!_" The child in Chrome's arm cried out, struggling to escape. Tsuna quickly grabbed him, holding him carefully.

"Not right now, Lambo-kun! Dinner's not served yet!" He chided the child, too distracted to stop Reborn from letting go of Chrome's hand to tug at Sena's shirt.

"Chaos," Reborn greeted, his eyes – too sharp for a child – piercing into Sena. He seemed to be looking down at Sena, despite his much-shorter stature. "You look just as _Dame_ as Tsuna."

Sena's jaw dropped at his words, spluttering as he tried to find a way to retaliate without offending the child—or making him seem like a bad person in Chrome's eyes. "H-hey… isn't that a bit harsh?" He asked, trying not to pout at the judgement. "I'm not _dame_… not anymore!"

Reborn looked at him from head to toe, making Sena squirm in embarrassment. He then smirked. "Tch… at least you're less scrawny than Tsuna. Want to play a game with me?" He added suddenly.

The non sequitur made Sena blink, looking confused. "S-sure? What's the game called?" He asked.

Reborn's smirk widened into an evil grin, sending shivers down Sena's spine. Oh god… what had he agreed to?

"It's called the _mafia game_—"

Tsuna nervously put himself between Reborn and Sena before Reborn could say anymore. "_Well_, Sena, you've met all of my best of friends!" He exclaimed, letting Chrome take Lambo out of his arms so that he could begin to push Sena away from his friends. "I suppose you can call them my _family_, now, because of how close we are…"

Sena could tell that Tsuna was trying distract him from Reborn's creepy behaviour, and he was rather thankful that his cousin was giving him an escape route. The kid, though young, was someone he didn't want to cross at all.

He had this feeling that Reborn was more trouble than he looked.

But he couldn't help but wonder, was that how Hiruma or Agon were as children? Creepy and overly precocious? He shuddered again at the thought of the baby-devils that his mind conjured up as an image. Hiruma would've been a child that even his own mother would fear...

But he quickly shook himself of these thoughts.

"Is that why you brought them over?" Sena asked, looking over his shoulder to glance at Chrome one last time—only she was now under the protective embrace of Mukuro. Were they siblings? he wondered, noting the similarities they had between them.

They both had purple-black hair, with one eye that was different to the other (Chrome had a rather fetching eye-patch, and he couldn't help but wonder what had happened to the girl), and though Chrome was a lot more timid than Mukuro… they seemed to exude the same mysterious air. Not to mention, they were both very attractive…

But Sena's thoughts were quickly interrupted by Tsuna's voice, and he turned to look at him again.

"Y-yeah… I suppose you can say that," Tsuna agreed. Sending him another grin, he nudged Sena lightly. "Say, why don't you introduce me to _your_ American football friends? It isn't fair that you get to meet my friends, while I haven't met yours!"

Sena's lips curled into a nervous smile, unable to _not_ agree when faced with Tsuna's expectant doe-eyes. "A-alright…" he mumbled in defeat, wondering just how long it would take before Hiruma chased Tsuna away in fear.

Tsuna beamed once again, before giving him a tight hug. "Why don't you grab a table with your parents? I'll get my mum and the rest of my friends to join you guys – we can finally have a table for ourselves!" He exclaimed, looking rather cheerful at the thought.

Sena couldn't help but agree. At least this year, they wouldn't have to put up with snobby family members looking down at both Tsuna and Sena…

And if Tsuna somehow got Chrome-san to sit next to him, that made the slight victory all the sweeter.

* * *

**A/N:** I like to think that Sena gets infatuated with girls who have similar personalities to his own, such as Karin. But in the end, he's the kind of guy that needs someone who's confident enough to make sure that Sena knows that he's worth it too.

So that's why Amefuto players are so much better for him (though really, Sena and Hibari are hilarious couple to consider), rather than Chrome. (But don't get me wrong: I love her to bits!)


End file.
